by no means is this the definitive answer but:I beleive you can advertise your clan in IRC telling people about what your clan is for/about but as long as you are not posting 'join my clan XXX' over and over again or PM Spamming both of those are against the rules.

DD - Ideas Guru

Global rank 728(as of March 27th)Currently Selling: M.Diglett, M.Vulpix, Buying: NothingQuest: to get one of every pokemon. Currently training: 316 - Gulpin

Also, do not spam the !invite command. What I mean is don't !invite Shohs five times. If the user wants to join, they would do it. I've actually seen someone get banned from the IRC server itself for doing that.